Learning Few-shot Segmentation from Bounding Box Annotations

We present a new weakly-supervised few-shot semantic segmentation setting and a meta-learning method for tackling the new challenge. Different from existing settings, we leverage bounding box annotations as weak supervision signals during the meta-training phase, i.e., more labelefficient. Bounding box provides a cheaper label representation than segmentation mask but contains both an object of interest and a disturbing background. We first show that meta-training with bounding boxes degrades recent few-shot semantic segmentation methods, which are typically meta-trained with full semantic segmentation supervisions. We postulate that this challenge is originated from the impure information of bounding box representation. We propose a pseudo trimap estimator and trimap-attention based prototype learning to extract clearer supervision signals from bounding boxes. These developments robustify and generalize our method well to noisy support masks at test time. We empirically show that our method consistently improves performance. Our method gains 1.4% and 3.6% mean-IoU over the competing one in full and weak test supervision cases, respectively, in the 1-way 5-shot setting on Pascal-5(i).